1. Field of the Invention
This invention relates to a drilling fluid additive system manufactured by a process comprising: admixing colloidal solids with a carrier to create a suspended mixture to thereby allow the solids to be pre-wet or coat with the carrier; admixing copolymer beads to the suspended mixture to thereby allow the beads to be pre-wet or coat with the carrier and to form a drilling fluid additive mixture; and admixing hydrophilic clay, a pH controller, a fluid loss controller, and a dispersant to the drilling fluid additive mixture. More specifically, the present invention relates to an improved method of enhancing the surface of a cake wall of a well bore by adding a drilling fluid system to the well bore manufactured by the following method: admixing talc with an oil or glycol and then admixing polymer beads to the mixture, and subsequently adding this mixture with a mixture of hydrophilic clay, a pH controller, a fluid loss controller, and a dispersant.
2. Description of the Related Art
New technology in drilling for oil and gas now includes horizontal drilling. The horizontal drilling concept exposes more surface area of the producing zone than the conventional vertical drilling operations. For example, if a producing zone is fifty feet in thickness and a vertical well is drilled through such a zone, then only fifty feet of the producing zone will be exposed for production. In contrast, a horizontally drilled well may penetrate the producing sand or zone by one thousand feet or more. The amount or volume of oil or gas production is directly proportional to the horizontal penetration in feet into the producing sand or zone. In horizontal or directional drilling where the drill pipe must bend in order to achieve the desired penetration into the producing zone, friction becomes a major problem. The primary source of friction is directly related to the adhesion of the drilling assembly to the wall cake which lines the drilled well bore. The capillary attractive forces generated by the adhesion of the drilling assembly to the wall cake are directly proportional to the amount or footage of the drilling assembly exposed to the surface of the wall cake.
In horizontal or directional wells, many methods have been used in order to reduce friction between the drilling assembly and the wall cake. One such method would be to add a liquid lubricant to the drilling fluid in order to reduce the coefficient of friction of the drilling fluid. These liquid lubricants include oils, such as hydrocarbon based oils, vegetable oils, glycols, etc. These liquid lubricants will usually reduce the coefficient of friction of the drilling fluid resulting in a reduction of friction between the drilling assembly and the wall cake of the well bore.
When the liquid lubricant is added to the drilling fluid, it has several options as to how it will react. One option is that the lubricant remains isolated and does not mix well with the drilling fluid. A second option is that the lubricant emulsifies with the water in the drilling fluid to form an oil-in-water emulsion. Still another option is the oil attaching itself to the commercial solids in the drilling fluid or to the drilled cuttings or drilled solids. In certain circumstances, some of the liquid lubricant might be deposited or smeared onto the wall cake of the well bore. The ideal scenario would be to have all of the liquid lubricant deposited on the wall cake.
Those experienced in drilling fluid engineering know that a thin, tough, pliable, and lubricious wall cake is most desirable. The integrity of a wall cake is determined by several factors. The thickness of a wall cake is directly proportional to the amount of liquid leaving the drilling fluid, and being forced into the wall of the well bore by hydrostatic pressure. The thickness of the wall cake is also determined by the type and particle size of the solids in the drilling fluid. Particle Size Distribution, or PSD is important to the wall cake integrity. Experts in drilling fluids also know that materials such as bentonite clay, starches, lignites and polymers are all used to build acceptable wall cakes. It is known in the prior art that various food grade vegetable oils are acceptable lubricants when used alone in water-based drilling fluids. It is also known in the prior art that round co-polymer beads when used alone in water-based drilling fluids function as a good friction reducer. However, much more is required to improve the wall cake integrity and lubricity of most well bores. In addition, there is no technology or process in the prior art that improves the lubrication or friction reducing capacity of the copolymer beads.
Furthermore, the solids control equipment used on the drilling rigs today is far superior as to what was used 15 to 20 years ago. In the past, drilling rig shale shakers would probably be limited to screen sizes of about 20-40 mesh on the shakers. These coarser mesh screens would allow pieces of shale and the drilled formation to pass through the shaker screens back into the drilling fluid and then recirculated back down the well bore. As these larger than colloidal size particles make their way back up the well bore to the surface, the action of the drilling assembly rotating within the well bore forces these larger particles into the surface of the well bore. For example: a 20xc3x9720 mesh shaker screen would allow a drilled cutting sized at 863 microns or 0.0340 inches to pass through it and then the cutting would be returned to the well bore and some of these 863 micron cuttings would eventually be embedded into the wall cake. This would give the wall cake surface a texture resembling that of coarse sandpaper. These larger particles would allow the drilling fluid to channel and pass between the drilling assembly and the wall cake thereby reducing the negative effect of the capillary attractive forces generated by the close contact of the drilling assembly with the wall cake. The instances of the drilling assembly becoming stuck to the wall cake when less efficient solids control equipment, such as shale shakers, was used much less than it is today. The more efficient shale shakers today are a great improvement for the drilling fluids but the instances of sticking the drilling assembly are higher. The reason for a higher rate of stuck drilling assemblies today could be blamed on cleaning the drilling fluid to efficiently. Today many drilling rigs utilize cascading shale shakers, which eventually pass the drilling fluid through 200 mesh or 74 micron screens. This is very positive for controlling the percentage of drilled solids in the drilling fluid but it also affects the texture or surface of the wall cake. The finer the solids on the surface of the wall cake are, the greater the capillary attractive forces will be between the drilling assembly and the wall cake.
The present invention provides a method of enhancing the surface of the wall cake. In order to accomplish this, the invention provides a method, which adds something to improve the texture of the surface of the wall cake, and then adds something to prevent large amounts of water from leaving the drilling fluid then passing through the wall cake into the formation. The present invention also provides a carrier for the colloidal solids and beads, which also acts as a lubricant for the drilling fluid. The present invention further provides a process that reduces the effect of capillary attractive forces between the drilling assembly and the wall cake, thereby reducing the tendency of the drilling assembly to become stuck. In high angle directional wells where down hole motors are used to rotate the drill bit and the drill pipe remains stationary, it is important that the drilling assembly can slide as the drilling bit cuts more holes. The present invention improves the ability to slide while drilling as stated above.
In one embodiment, the present invention relates to a drilling fluid additive system manufactured by a method comprising of: admixing colloidal solids with a carrier to create a suspended mixture to thereby allow the solids to be pre-wet with the carrier; admixing copolymer beads to the suspended mixture to thereby allow the beads to be pre-wet with the carrier and to form a drilling fluid additive mixture, the solids and the beads having an affinity for oils, esters, glycols and olefins; and admixing hydrophilic clay, a pH controller, a fluid loss controller, and a dispersant to the drilling fluid additive mixture.
For purposes of this invention, the carrier applies to both the liquid and solid (powder) forms of carrier and the term pre-wet or coat shall apply to dry and wet coatings and/or treatments of the solid with the carrier. In one embodiment, the talc is pre-wet with a liquid carrier. In another embodiment, the talc is coated with a solid (powder) carrier.
In another embodiment, the beads are comprised of styrene and divinylbenzene. In still another embodiment, the beads have a specific gravity at about 1.0 and a size from about 100 microns to about 900 microns. In yet another embodiment, the solids are comprised of talc. In still yet another embodiment, the solids have a size range from about 2 microns to about 10 microns.
In a further embodiment, the carrier may consist essentially of oils, vegetable oils, mineral oils, paraffin oils, animal oils, esters, glycols and olefins. In yet a further embodiment, the carrier functions as a lubricant. In still a further embodiment, the carrier comprises soybean oil.
In yet still a further embodiment, the carrier of the present invention comprises polypropylene glycol. In another further embodiment, the carrier comprises from about 5% to about 98% of the additive mixture, the solids comprises from about 2% to about 50% of the additive mixture, and the beads comprises from about 2% to about 50% of the additive mixture.
In yet another further embodiment, the system further comprises a weighting agent, the weighting agent consisting essentially of barium sulfate (barite), calcium carbonate, hematite, and salts. In still yet another further embodiment, the system further comprises a surfactant, the surfactant being a nonionic surfactant. In another embodiment, the surfactant comprises a polyethoxylated glycol.
In still another embodiment, the pH controller may consist essentially of caustic acid, lime, potassium hydroxide and sodium hydroxide. In yet another embodiment, the fluid loss controller may consist essentially of lignites, polyacrylamide and graphite uintaite (Gilsonite) glycol dispersions. In still yet another embodiment, the hydrophilic clay may consist essentially of bentonite, kaolin clay and viscosifiers. In a further embodiment, the dispersant may consist essentially of lignite and lignosulfonate. In yet a further embodiment, the system further comprises a chemical inhibitor, the chemical inhibitor consisting essentially of gypsum, lime, potassium chloride, potassium hydroxide, magnesium sulfate and calcium sulfate.
In another embodiment, the present invention relates to a method of manufacturing a drilling fluid additive system, the method comprising: shearing colloidal solids with a carrier to create a suspended mixture to thereby allow the solids to be pre-wet with the carrier and to form a drilling fluid additive mixture; and admixing hydrophilic clay, a pH controller, a fluid loss controller, and a dispersant to the drilling fluid additive mixture. In one embodiment, the solid may be admixed with the carrier and in another embodiment, the solid may be sheared with the carrier. In one embodiment, the solid may be admixed with the carrier and in another embodiment, the solid may be sheared with the carrier.
In yet another embodiment, the method further comprises admixing polymeric beads to said drilling fluid additive mixture after pre-wetting said solids with said carrier, said solids and said beads having an affinity for cellulose, oils, esters, glycols and olefins. In still another embodiment, the beads have a specific gravity at about 1.0 and a size from about 100 microns to about 900 microns; the beads are comprised of styrene and divinylbenzene. In still yet another embodiment, the solids have a size range from about 2 microns to about 10 microns; the solids are comprised of talc. In a further embodiment, the carrier consists essentially of oils, vegetable oils, mineral oils, paraffin oils, animal oils, esters, glycols and olefins.
In yet a further embodiment, the carrier comprises polypropylene glycol. In still a further embodiment, the carrier comprises soybean oil. In another further embodiment, the solids comprises from about 2% to about 50% of the additive mixture; the carrier comprises from about 5% to about 98% of the additive mixture; and the beads comprises from about 2% to about 50% of the additive mixture.
In yet another further embodiment, the pH controller may consist essentially of caustic acid, lime, potassium hydroxide and sodium hydroxide. In still another further embodiment, the fluid loss controller may consist essentially of lignites, polyacrylamide and graphite uintaite (Gilsonitexe2x80x9d) glycol dispersions. In still yet another further embodiment, the hydrophilic clay may consist essentially of bentonite, kaolin clay and viscosifiers. In another embodiment, the dispersant may consist essentially of lignite and lignosulfonate.
In yet another embodiment, the method further comprises adding a weighting agent; the weighting agent consisting essentially of barium sulfate (barite), calcium carbonate, hematite, and salts. In still another embodiment, the method further comprises adding a surfactant; the surfactant being a nonionic surfactant. In still yet another embodiment, the method further comprises adding a chemical inhibitor; the chemical inhibitor consisting essentially of gypsum, lime, potassium chloride, potassium hydroxide, magnesium sulfate and calcium sulfate.
In a further embodiment, the present invention relates to a method of enhancing the surface of a wall cake of a well bore; the method comprising: shearing colloidal solids with a carrier to create a suspended mixture to thereby allow the solids to be pre-wet or coated with the carrier; admixing copolymer beads to the suspended mixture thereby allowing the beads to be pre-wet or coated with the carrier; adding the suspended mixture to a water-based drilling fluid to form a system, the drilling fluid comprising hydrophilic clay, a pH controller, a fluid loss controller, and a dispersant; and adding the system to a well bore.
In yet a further embodiment, the beads having an affinity for oils, esters, glycols, cellulose and olefins; the beads have a specific gravity at about 1.0 and a size from about 100 microns to about 900 microns; the beads are comprised of styrene and divinylbenzene. In still a further embodiment, the solids having an affinity for oils, esters, glycols and olefins; the solids have a size range from about 2 microns to about 10 microns; the solids are comprised of talc. In still yet a further embodiment, the carrier may consists essentially of oils, vegetable oils, mineral oils, paraffin oils, animal oils, esters, glycols and olefins; the carrier may function as a lubricant. In a further embodiment, the drilling fluid further comprises a surfactant; the surfactant comprises a polyethoxylated glycol. In another further embodiment, the drilling fluid further comprises a weighting agent; the weighting agent consisting essentially of barium sulfate (barite), calcium carbonate, hematite, and salts. In another embodiment, the solids comprises from about 2% to about 50% of the additive mixture; the carrier comprises from about 5% to about 98% of the additive mixture; and the beads comprises from about 2% to about 50% of the additive mixture.
In another embodiment, the present invention relates to a water-based drilling fluid additive comprising talc and at least one carrier wherein the carrier may be oils, esters, glycols, cellulose and olefins or combinations thereof. In still another embodiment, the talc is coated or treated with the carrier converting the surface of the talc to a carrier treated or coated surface.